1. Technical Field
The present invention relates to pre-crash sensing systems for automotive vehicles, and more particularly, to pre-crash sensing systems for enabling and disabling vehicle safety countermeasures operated in response to pre-crash detected imminent crash.
2. Background
Auto manufacturers are investigating radar, lidar, and vision-based pre-crash sensing systems to improve occupant safety. Current vehicles typically employ accelerometers that measure decelerations acting on the vehicle body in the event of a crash. In response to accelerometers, airbags or other safety devices are deployed.
In certain crash situations it would be desirable to provide information before forces actually act upon the vehicle when a collision is unavoidable.
Remote sensing systems using radar, lidar or vision based technologies for adaptive cruise control, collision avoidance and collision warning applications are known. These systems have characteristic requirements for false alarms. Generally, the remote sensing system reliability requirements for pre-crash sensing for automotive safety related systems are more stringent than those for comfort and convenience features, such as, adaptive cruise control. The reliability requirements even for safety related features vary significantly, depending upon the safety countermeasure under consideration. For example, tolerance towards undesirable activations may be higher for activating motorized belt pre-tensioners than for functions such as vehicle suspension height adjustments. Non-reversible safety countermeasures, including airbags, require extremely reliable sensing systems for pre-crash activation. However, the size of objects is typically not taken into consideration in the activation of such countermeasure devices. Also, such systems may generate unintentional or undesirable activations when acting at high speeds, low speeds, or in curve situations. When a vehicle is traveling on a curved road, for example, objects outside of the lane of travel may be determined to be potential crash objects.
It would therefore be desirable to provide a pre-crash sensing system that reduces unintentional or undesirable activations and improves the reliability of object detection and threat assessment. It would also be desirable to provide a system that takes into consideration the size of the object detected.
The present invention provides an improved pre-crash sensing system that reduces false activations and activates a countermeasure in response to the size of the object detected.
In one aspect of the invention, a control system for an automotive vehicle has a remote object sensor that generates an object signal in the presence of an object. A vehicle trajectory sensor generates a signal corresponding to the potential presence of a curved road. A vehicle speed sensor generates a speed signal corresponding to the longitudinal speed of the vehicle. A controller is coupled to the remote object sensor, the vehicle trajectory sensor, and the vehicle speed sensor. When the remote object sensor indicates the presence of an object with a minimum cross section in a predefined decision zone, and meeting relative velocity based criteria, and the vehicle speed is above a first minimum threshold and below a second maximum threshold and said road trajectory signal indicates a curved road with the radius of curvature over a pre-selected value, a countermeasure system is activated.
In a further aspect of the invention a method for operating a control system comprises:
establishing a first speed threshold and a second speed threshold;
generating a speed signal corresponding to a vehicle speed; and
disabling the countermeasure system when the vehicle speed is below the first threshold or above said second threshold.
One advantage of the invention is that the size and orientation of the sensed object may be taken into consideration. This is extremely useful if the object is another automotive vehicle such as a sport utility, car or truck. By knowing the size of the vehicle, different countermeasures and different countermeasure activation modes may be chosen. Another advantage of the invention is that unintentional or inadvertent activation of countermeasure devices is minimized.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.